Prior portable water purification systems consist of iodine or chlorine tablets, particulate filters, iodophors, reverse osmosis filters, and various combinations of these elements. Iodine and chlorine tablets are primarily useful for treating low levels of biological contaminants. Residue from tablets results in undesirable water taste and possibly produces health side effects. Particulate filters only remove solid particles from the water. Reverse osmosis systems are primarily designed to address desalination.
Although more extensive systems which remove a broad range of contaminants exist, such systems are extremely large, not portable and require significant outside energy inputs.
The pumping means for these prior systems generally consists of simple plunger or piston-type pumps, diaphragm-type pumps, and complex regenerative piston or diaphragm pumps. In these pump mechanisms, the regenerative fluid is fed directly onto the backside of the pump piston or diaphragm. Thus, the force regeneration, and, thus, the ratio of permeate to concentrate, from the reverse osmosis filter, is always linear. Also, prior pumps include a mechanical dwell in the piston or diaphragm motion during directional valve actuation as an essential mechanical function. However, this dwell introduces a fluctuating force requirement to the pump handle or lever. Furthermore, numerous seals and springs in prior pumps are in direct contact with concentrated brine, which can lead to a buildup of contaminants on the surfaces and rapid aging or failure. In addition, the concentrated brine of the reverse osmosis filter is in direct contact with the pump cylinder and separated from the feed water by a moving seal between the piston and cylinder wall. This arrangement can lead to cross-contamination when dealing with nuclear, biological or chemical contaminants.
Therefore, a need exists for a water purification system which is capable of refining water contaminated with nuclear, biological, chemical and other contaminants. Furthermore, a need exists for a lightweight, portable system which can be used for military service, emergency and disaster relief efforts, backpacking and camping, and in travel to foreign countries where the domestic water supply is substandard and contaminated. Furthermore, a need exists for a purification system which has desalination capability for use in a sea water environment.
A need also exists for a pump mechanism which can allow variable ratios of permeate to concentrate. A need exists for a pump system which reduces the level of contaminants contacting the seals and other parts of the pump. Finally, a need exists for a pump mechanism which prevents cross-contamination of feed water and concentrate.